General and Robust Photothermal-Heating-Enabled High-Efficiency Photoelectrochemical Water Splitting

The ability of photoanodes to simultaneously tailor light absorption, charge separation, and water oxidation processes represents an important endeavor toward highly efficient photoelectrochemical (PEC) water splitting. Here, a robust strategy is reported to render markedly improved PEC water splitting via sandwiching a photothermal Co₃O₄ layer between a BiVO₄ photoanode film and an FeOOH/NiOOH electrocatalyst sheet. The deposited Co₃O₄ layer manifests compelling photothermal effect upon near-infrared irradiation and raises the temperature of the photoanodes in situ, leading to extended light absorption, enhanced charge transfer, and accelerated water oxidation kinetics simultaneously. The judiciously designed NiOOH/FeOOH/Co₃O₄/BiVO₄ photoanode renders a superior photocurrent density of 6.34 mA cm^–2 at 1.23 V versus a reversible reference electrode (V_RHE) with outstanding applied bias photon-to-current efficiency of 2.72% at 0.6 V_RHE. In addition to the metal oxide, a wide variety of metal sulfides, nitrides, and phosphides (e.g., CoS, CoN, and CoP) can be exploited as the heaters to yield high-performance BiVO₄-based photoanodes. Apart from BiVO₄, other metal oxides (e.g., Fe₂O₃ and TiO₂) can also be covered by photothermal materials to impart significantly promoted water splitting. This simple yet general strategy provides a unique platform to capitalize on their photothermal characteristics to engineer high-performing energy conversion and storage materials and devices.